1. Field of the Invention
This invention relates to an interconnection assembly used for a motor of, e.g., an electric car to connect with the motor coil wire, and relates to a method of making the same.
2. Description of the Related Art
Conventional interconnection assemblies used to connect with the motor coil wire are made as follows. At first, a square copper plate 24 as shown in FIG. 1A is punched by pressing as shown in FIG. 1B, thereby giving a lead frame as shown in FIG. 1C. Then, as shown in FIG. 2, four lead frames 21 for U phase, V phase, W phase and grounding are stacked with a gap of about 0.5 to 2 mm in the vertical direction Finally, as shown in FIG. 3, the lead frame 21 is placed in a molding die (not shown) and is then molded with super-engineering molding resin 27.
The motor coil wire (not shown) is connected to a terminal 22 of the lead frame 21. The connecting method available is in general spot welding (fusing), soldering etc. The super-engineering molding resin available is polyphenylsulfide (PPS), liquid crystalline polymer (LCP) etc.
In FIG. 3, of twelve terminals 22, six terminals are for grounding and each two of the remaining six terminals are assigned to U phase, V phase and W phase. 23, 23 and 23 are terminal connectors for U phase, V phase and W phase.
If in a large motor the diameter of stator becomes greater than 150 mm, the dimension of interconnection assembly to be used increases and the amount of current to be flown increases. Because of this, temperature of the lead frame 21 rises and temperature of the molded resin 27 also rises. In this case, there occurs a large strain between the copper lead frame 21 and the PPS resin 27 since resin 27 around the lead frame 21 is closely contacting the lead frame 21 due to a high injection pressure in molding and there is a difference in linear expansion coefficient between the copper lead frame 21 and the PPS resin 27.
In motors, especially then it starts and during the normal operation, the current-carrying capacity changes severely. Thus, when the current-carrying capacity changes severely, there may occur a crack in the molded resin 27 that is mechanically weak and has a great expansion coefficient and, therefore, the insulation performance may be broken.
Furthermore, as shown in FIG. 1B, when the copper plate 24 is punched by pressing or cut, waste part 25 is necessarily generated. Thus, loss of material increases and lowering of yield causes an increase in manufacturing cost. Especially in large interconnection assembly, the waste part 25 further increases since the copper plate 24 must have a greater size and thickness.